Abstract: Inspired by the homogenization theory in the field of micromechanics, a regular triangular prism-quasi-inscribed sphere unit cell model at the meso-scale for predicting the thermal conductivity of two-phase (dry or water-saturated) geomaterials is proposed by using the lumped parameter thermo-electric analogy method. The performance of the established model is evaluated with 34 sets of thermal conductivity experimental data and 238 sets of thermal conductivity predictions. The results indicated that: (1) The regular triangular prism-quasi-inscribed sphere unit cell is a real representative elementary volume that can characterize the macroscopic continuum geomaterials and overcome the inherent spatial correction defects of the sphere and cylinder unit cell structures. Besides, this model can be used for soil-rocks with the porosity of 0~0.6, covering most porosity range of the natural geomaterials. (2) The MATLAB data visualization illustrate that the proposed model gives thermal conductivities concavely decreasing with porosity, and the model performance is better at relative high porosity (0.3~0.6) than those at low void ratio (< 0.25). (3) Taking the typical geomaterials under two-phase condition as an example, this model has better predictive performance than other unit cell theoretical models, especially under dry condition (the RMSE and NRMSE are, respectively, 0.89W/(m·K) and 31%). (4) Finally, the unit cell model proposed herein can be extended to three-phase unsaturated state (general solid-liquid-gas), and a promising initiative, i.e., to study the effects of component and structure on the effective thermal conductivity of porous- granular geomaterials from an evolutionary perspective, is conjectured based on pore/particle structure and pore water morphology, aiming to provide a new way for further investigating the macroscopic thermo-mechanical behavior of tanglesome geomaterials.